Open Access Dissertation
Date of Award
Physics and Astronomy
Soft matter is a subfield of condensed matter physics that includes the study of colloidal dynamics. This is important in multidisciplinary fields for technological and medical advancements. My research focused on quantifying the dynamics of nano and micron-sized particles within various media using two-photon fluorescence correlation spectroscopy (FCS) and differential dynamic microscopy (DDM). FCS is a single photon sensitive technique that detects spontaneous fluctuations in fluorescence during dynamical processes over time while DDM used optical microscopy to analyze the colloidal motion in Fourier space. The diffusion coefficient (D) of 25 nm radii particles within aqueous entangled solutions of polyethylene oxide (PEO; Mw=600 kg/mol) demonstrated normal diffusion with almost identical values using DDM and FCS and followed a scaling theory. We observed characteristic peaks in relaxation time τ(q) of microdiscoids dispersed in aqueous water lutidine solutions that indicate slow relaxations in certain structural rearrangements explained with de Gennes narrowing phenomenon. Melting of the crystal structures formed by microdiscoids on top of droplets is comparable to a 2D melting theory. In case of microellipsoids (aspect ratio ≈2.8), DDM is proven to be a quick and powerful method to determine the translational and rotational diffusion coefficients.
Shokeen, Namita, "Colloidal Dynamics Within Polymer Solutions And Complex Fluids" (2019). Wayne State University Dissertations. 2308.